Bladed rotors and stators



Aus. 12, 1958` 1 ISUP y 2,847,184

BLADED ROTORS AND STATORS Filed March 50, 1953 A 2 Sheets-Sheet l F IG.3.

Aug.l 12, 1.958 L. lsLlP BLADED RoToRs AND sTAToRs 2 sheets-sheet `2Filed March 50, 1953 L, Attornrys United States Patent Office 2,847,184Patented Aug. 12, 1958 BLADE'D ROTRS AND STATORS Leonard Islip, Cove,Farnborough, England, assignor to Power Jets (Research and Development)Limited, Lon

This invention relates to the construction of bladed rotors, forexample, for axial flow turbines and more particularly for axial flowcompressors. The object of the invention is to provide a rotorconstruction which is cheap and light, and suitable for rapid massproduction. The construction is not necessarily intended to be suitablefor use in steam and gas turbines intended for operation at hightemperatures.

A further object of the invention is the provision of a statorconstruction which will similarly be cheap and light, and easy to make.

Accordingly, the invention provides a bladed rotor comprising a rotorelement made up of at least one sheet metal disc having a peripheralflange, and a row of sheet metal blades mounted on said flange.

According to a feature of the invention the blades are tubular and havetheir root ends flared out to form a lateral skirt seating on andsecured to the rotor disc flange. According to a further feature, therotor element is made up of two flanged sheet metal discs arranged backto back .and the blades are secured to the flanges of both discs.

The stator similarly comprises a sheet metal casing having a row ofsheet metal blades attached thereto. According to a feature of theinvention, the stator blades are tubular and have their ends flared outto form skirts which seat on and are secured to the stator casing. Inone form of the invention, the stator casing is formed with holes intowhich the ends of the blades are inserted and the skirts are secured tothe outer surface of the casing, and in another form, the skirts areseated upon and secured to the inner surface of the casing.

The other ends of the stator blades may be similarly formed with skirtsfor attachment to a shroud ring.

Two embodiments of the invention will now be described with reference tothe accompanying drawings, of which:

Figure l is an axial half-section of the outlet end of a multistagecompressor rotor and stator.

. Figure 2 is a fragmentary section on the line II-II in Figure 1.

Figure 3 is a fragmentary developed section on the line III-III inFigures 1 and 2.

Figure 4 is an axial half-section of the outlet end of a secondmultistage compressor rotor and stator.

Figure 5 is a fragmentary developed view on the line V-V in Figure 4.

Referring to Figure 1, the rotor comprises -a number of co-axial,axially spaced rotor elements, each of which is made up of two sheetmetal discs 1, 2. These discs have their peripheries turned over to forma channelshaped rim, that is, they each have a cylindrical flange 1a, 2aof the same width around the discs and a radially inwardly projectingannular portion 1b, 2b. The two discs are fastened together back to backby rivets (as shown) or bolts, or by welding or brazing or the like.

Attached to the outer surface of the disc flanges lis a row of hollowsheet metal blades 3. Each blade is a length of tube of the requiredaerofoil cross-section and twisted if necessary as required by thedesign. The tube is slit along its leading and trailing edges for adistance equal to about half the desired root spacing between adjacentblades, and the two separated parts thus formed are bent outwards fromeach other to form lateral skirts 3a extending approximately at rightangles to the axis of the blade. These skirts seat upon the rotor discflanges 1a and 2a, and they are cut to such a length that the skirts onadjacent blades abut with one another (as shown in Figures 2 and 3), andto such `an angle that the blades are thereby set at the desired spacingand stagger angle.

Between each pair of adjacent blades there is provided a sheet metalreinforcing strip 4. On two of the discs this strip is channel shaped,the base being of such a length that it just spans the flanges 1a, 2a ofthe rotor discs, while the sides 4a of the channel bear against theinturned portions 1b, 2b of the rotor discs. The strip has its edgesshaped in conformity to the profile of the blades on each side thereof,so that when placed in position it just fills the space between theblades as shown in Figure 3. The strips on each side of each blade meetat the leading and trailing edges thereof. The underside of the stripsare bevelled along the edges to accommodate the fillets at the base ofthe blades.

The strips 4 and the blade skirts 3a are secured to the rotor flanges bycountersunk rivets 5. The side portions 4a of the reinforcing strips arealso secured by rivets 6 to the in-turned portions 1b, 2b of rotordiscs. The reinforcing strips 4 thus reinforce the blades againstcentrifugal force and oppose the tendency for the fillets at the bladeroots to ybe pulled out straight. The blades are so disposed on the discflanges that the radi-al plane in which the centrifugal loads actcoincides with the joint face of the two rotor discs 1, 2, so that therewill be no bending movements tending to bend the discs over in an axialdirection. The inturned parts 1b, 2b of the rotor discs reinforce theflanges 1a, 2b, and oppose the tendency for them to bell out undercentrifugal force. The strip 4b, on the left-hand disc is however ashereinafter described with reference to Fig. 4.

Adjacent rotor elements are separated by channel-section annular spacers7, the flanges of which abut with the rotor elements. The spacers are ofsuch a width that a space is left between the rotor flanges for thestator blade shroud as will be described below.

At each end of the rotor, there is provided a frusto conical bearermember 8 to which is attached, for example, by welding, a stub shaft 9for support in bearings. The bearer members 8, the rotor elements andspacer elements 7 are all threaded on to a number of (say eight) tierods 10 symmetrically disposed around the rotor axis and extending thelength of the rotor, and are held together by nuts 10a on the ends ofthe tie rods.

When building up the rotor, each rotor element is first built up as asub-assembly. The two rotor discs 1, 2 are placed back to back andriveted or otherwise fastened together, and then the blades 3 andreinforcing strips 4 are attached to the rotor disc flanges 1a, 2a.There may be some difficulty in getting to the inside of the flanges 1a,2a and inturned portions 1b, 2b of the discs for holding the rivets, andso sOme form of blind rivetting process may be used. The rivets could bereplaced by spot welding.

The built-np rotor elements, the spacers 7 and the bearer-members 8 areassembled by simply threading them in order on to the tie rods 10, andtightening up with the nuts 10a.

The spacers 7 can be reinforced against buckling whenI tightening up thenuts a by distance pieces 19 threaded on to the tie rods 10 and lyingbetween the sides of the spacers.

The stator is made up of a number of axially abutting frustoconicalsheet metal liner members 11, each carrying a row of tubular sheet metalstator blades 12. The liner is formed with holes into each of which theend of a blade is inserted. This blade end is formed with tabs 12awhich, after the blade is inserted in the hole, are turned over at rightangles to the blade and are brazed or welded to the outside ofthe liner.The inner ends of the row of blades are joined by a sheet metal shroudring 13, which is formed with holes into which the other ends ofthestator blades fit. These ends' of the blades are also formed with tabs12b which are turned over and brazed or welded to the inside of theshroud ring in the same way as the tabs 12a are secured to the liner 11.The shroud rring is channel shaped in cross section; the upstream side13a is somewhat longer than the downstream side 13b and co-operates withthe inturned portion on the adjacent rotor disc to form a knife-edgeseal preventing leakage around the shroud ring.

The liner 11 and shroud ring 13 of each row of blades are split on thesame diametrical plane. Thus each row of blades is made up of twosegments which t together around the rotor. For convenience inmanufacture the row of blades might be divided into a greater number ofsegments.

The liners are enclosed by a sheet metal outer casing 14. This casing isalso split on a diametrical plane and is provided with axial flanges 15along the split for bolting the two halves together `and with flanges 16at each end for. attachment to the adjoining inlet and outlet ducts. Thecasing is formed with circumferential corrugations 14a behind each rowof stator blades, which serve to stiffen the casing and also toaccommodate the tabs 12a whereby the blades are fastened to the liner.The casing and liners taper towards the outlet end of the compressor toprovide the necessary reduction in the cross-sectional area availablefor the air flow.

When assembling the stator, the blade row segments are fitted into thetwo halves of the outer casing 14, and then the casing is boltedtogether around the rotor. Liners 11 may be spot-welded to casing 14.

The rotor shown in Figure 4 is in general similar to that of Figure l,and the same reference numerals have been used for corresponding parts.The rotor discs 1, -2 are formed with axially extending peripheralflanges 1a, 2a, but the outer ends of these flanges are not reinforcedby iii-turned portions as in the first embodiment. The hollow sheetmetal blades have lateral skirts 3a seating upon the flanges 1a, 2a, andbetween each pair of adjacent blades there is a reinforcing strip 4b,which however difers from the reinforcing strip 4 of Figure l in that itis not of channel section but is merely a flat strip, the skirts,flanges and strips being welded-e. g. projection welded-or brazedtogether. The annular spacers 7 are channel shaped in section as beforebut t closely under the disc flanges. The spacers are somewhat widerthan the combined width of the two disc flanges which overlap them, sothat a circumferential recess is left between the ends of the flanges.The rotor discs 1, 2 and spacers 7 are held together by rings of nuts 17and bolts 18 symmetrically disposed around the rotor axis.

So as to reinforce the rotor blades in a circumferential sense, spacersare provided joining the tips of pairs of adjacent blades. As shown inFigure 5, one blade is formed with an integral extension 3b which isbent over in a circumferential direction and has its end secured e. g.by welding or brazing to the tip of the adjacent blade.

It is not intended that the rotor discs shall be provided with anycentral apertures for access to the spaces between the rotor elements.Accordingly it is necessary to secure either the nuts 17 or bolts 18 tothe spacers 7 be- 4 fore assembly. Thus the nuts 17 could be tack weldedto the inside of flange of the spacer 7, registering with the holestherein, the adjoining discs and spacers brought into abutmenttherewith, and the bolts 18 inserted.

The stator is generally similar to that shown in Figure l. However inthis embodiment, the liner members 11 and the shroud rings 13 are notformed with holes to receive the ends of the blades. Each stator blade12 is slit for a short distance at each end along the leading andtrailing edges, and the separated portions so formed are bent over toform lateral skirts 12C and 12d. These skirts seat upon and are securedto, e. g. by welding or brazing, the inner surface of the liners 11 andthe outer surface of the shroud rings 13. The skirts ofcircumferentially adjacent blades will be cut such a length as to abutwith one another and at such an angle that the stator blades are set atthe stagger angle required by the design. The shrouds 13 are simplecurved sheet metal strips, which coincide with the above-mentionedrecesses provided between the ends of the flanges on adjacent rotorelements.

Assembly of the stator will be the same as in the embodiment of Figurel.

Both the rotor and stator blades have been described above Vas beinglengths of tube of the appropriate aerofoil cross-section. However theycould be made from sheet material, bent to shape on a former and weldedalong the seam, for example, at the trailing edge, as shown at 3c inFigure 5. In this case the seam will be left unwelded at one or bothends as the case may be for a length corresponding to the width of theskirt or skirts, and a corresponding slit made in the leading edge.

The tips of the rotor blades are in any case left open;

it is believed that this will aid damping of blade vibration caused bythe air flow.

Suitable materials for both the rotor and stator and the blades would bealuminium or magnesium alloy, provided the compressor is intended tooperate only at fairly low temperatures. For higher temperatures, steelmight be used. In some circumstances it may be convenient to make therotor and stator from sheet steel while the 'blades are made ofaluminium alloy or magnesium alloy sheet. The construction of Fig. 4with parts brazed or Welded together is intended for use with blades,discs and re-inforcirrg strips of steel, and these parts would be ofsteel if they be brazed or welded as in the left-hand unit of Fig. l,but these parts would be rivetted together if one `or more of them weremade of one of the said alloys.

It will be seen that the discs 1 and 2 together form a wheel with acentral web through which passes the line of action of the centrifugalforce acting on the blades. The torque is transmitted by members 7 inFig. 4 and by these and rods 10 in Fig. l, so that in each case theinner part of each web is loaded only by the centrifugal force.

I claim: Y

l. A bladed rotor comprising two coaxial sheet metal discs havingcentral parts extending transversely to the rotor axis, `and havingtheir peripheries bent over to form flanges extending away from oneanother in a generally axial direction; a row of outwardly extendingtubular blades dispo-sed circumferentially around the rotor, each bladebeing of aerofoil cross-section and having a concave and a convex faceand being formed at its root end with a skirt extending from at leastone of said faces transversely to the blade axis and seating upon theouter surfaces of the flanges; a reinforcing strip superimposed upon askirt of a blade the edge of the strip being shaped to fit closelyagainst said face at its junction with the skirt; and means securingsaid strip and said skirt to the flange.

2. A bladed rotor comprising two coaxial sheet metal discs havingcentral parts extending transversely to the rotor axis and having theirperipheries bent over to form flanges extending away from one another ina generally axial direction; a row of outwardly extending tubular bladesof aerofoil cross-section disposed circumferentially around the rotor,each blade having a concave and a convex face and being formed on eachface at its root end with a skirt extending in a circumferentialdirection, said skirts seating upon the outer surface of the flanges andthe edges of skirts on circumferentially adjacent faces ofcircumferentially adjacent blades abutting with each other; areinforcing strip between each pair of circumferentially adjacent bladesand superimposed upon the abutting skirts, the edges of the strip beingshaped to fit closely against said faces at t-he junction with theskirts; and means securing said strips and said skirts to the anges.

3. A bladed rotor comprising two coaxial sheet metal discs havingcentral parts extending transversely to the rotor axis and having theirperipheries bent over to form firstly lianges extending away from oneanother in a generally axial direction and secondly inwardly extendingportions at the outer ends of the anges; a row of outwardly extendingtubular blades disposed circumferentially around the rotor, each bladebeing formed at its root end with a skirt extending in a circumferentialdirection on each side thereof, seating upon the outer surface of theanges and abutting at its edges with the edges of the skirts on thecircumferentially adjacent blades; a channel section reinforcing stripbetween each pair of circumferentially adjacent blades, the base of thechannel spanning the anges, being superimposed upon the abutting skirtsof the blades and being shaped at its edges to rit closely against theblades at their root ends, and the sides of the channel bearing oneagainst each of the inwardly extending portions of the discs; meanssecuring the base of the channel and the skirts to the flanges; andmeans securing the sides of the channel to the inwardly extending'portions of the discs.

4. A bladed rotor comprising a wheel having a peripheral rim and twoside surfaces; a row of outwardly extending tubular blades disposedcircumferentially around the rotor, each blade being formed at its rootend with a skirt extending in a circumferential direction on each sidethereof, seating upon the rim of the wheel and abutting at its edgeswit-h the edges of the skirts on the circumferentially adjacent blades;a channel section reinforcing -stn'p between each pair ofcircumferentially adjacent blades, the base of the channel spanning therim of the wheel and being superimposed upon the abutting skirts of theblades and being shaped at its edges to lit closely against the bladesat their root ends, and the sides of the channel bearing one againsteach of the sides of 6 the wheel; means securing the base of the channeland the skirts to the rim of the wheel; and means securing the sides ofthe channel to the sides of the wheel.

5. A bladed rotor comprising two coaxial sheet metal discs havingcentral parts extending transversely to the rotor axis and having theirperipheries bent over to form firstly anges extending away from oneanother in a generally -axial direction and secondly inwardly extendingportions at the outer ends of the anges; a row of outwardly extendingtubular blades disposed circumferentially around the rotor, each bladebeing formed at its root end with a skirt extending in a circumferentialdirection on each side thereof and seating upon the outer surfaces ofthe flanges; a channel section reinforcing strip between each pair ofcircumferentially adjacent blades, the base of the channel spanning theflanges and being superimposed upon the circumferentially adjacentskirts of the blades, and the sides of the channel bearing one againsteach of the inwardly extending portions of the discs; .means securingthe base of said channel and said skirts to the anges; and meanssecuring the sides of the channel to the inwardly extending portions ofthe discs.

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